Two wheel hand carts are well known in the prior art and are usually constructed of a metallic frame with components thereof secured in place or locked to the metallic frame for providing the necessary well known structure defining a two wheel hand cart. One typical prior art hand cart is disclosed in U.S. Pat. No. 4,563,014 wherein the primary cart frame includes one piece plastic cross rails secured to a metallic frame. Similarly, a prior art hand cart is disclosed in the Stallbaumer Reexamination Certificate B15,749,588 issued on Nov. 21, 2000 and U.S. Pat. No. 5,749,588 that discloses molded plastic side rails adapted to be secured to individual plastic cross rails. The reexamined Stallbaumer patent also discloses side rails in the form of individual open trusses, molded of a plastic, for carrying and distributing the cart loads. These molded plastic trusses were previously utilized for hand trucks but were constructed and formed of rigid materials such as disclosed in the Grieb U.S. Pat. No. 530,991 and the Knapp U.S. Pat. No. 1,192,790.
Grainger is a large distributor of industrial products that includes hand carts and trucks. The Grainger catalogue for carts and trucks is available on the internet and can be accessed at www.grainger.com. The Grainger catalogue includes convertible hand trucks constructed of steel, aluminum and composite materials. The Grainger model No. 4ZJ32 disclosed in the catalogue is partially constructed of plastic parts (not a simple plastic frame) including a transition attachment for converting the hand cart between two wheel and four wheel configurations utilizing the same handle for both configurations.
The prior art U.S. Pat. No. 4,563,014 suggests the construction of the basic frame for a hand cart to be fabricated of a single piece of a light weight sheet metal pressed into the desired shape. This patent also suggests the use of non-metallic plastic sheets for the basic frame but not further disclosed or detailed in the U.S. Pat. No. 4,563,014, see column 1, lines 63 and 64.
Various useful articles are known in the prior art that are fabricated completely of plastic including a single piece plastic bicycle frame per U.S. Pat. No. 5,533,742. Similarly, known hose storage apparatus is constructed entirely of plastic such as disclosed in U.S. Pat. No. Re. 32,510.
Whatever materials are selected to fabricate and form the structure of a hand cart, exclusive of the common wheel structures and handles, etc., the present day hand truck requires locking various sections such as cross rails and side rails to each other that with usage tend to result in the locked sections becoming lose including as a result of the tolerances built into the locked elements and thereby resulting in reducing the useful life of the hand cart, if not the complete breakage of the locked elements, such as the cross rails for the cart. To my knowledge, no all plastic frame for a hand cart is presently available that is commercially acceptable either in the form of a two wheel hand cart, four wheel hand cart or a hand cart convertible between the two wheel and four wheel configurations. Accordingly, there is a present need for a hand cart that has a one piece frame wherein all elements of the frame are formed in one integral part that eliminates the need for locking the various elements together and thereby eliminates the loosening of the locked elements for the frame so as to result in a hand cart of improved and longer useful life and a stronger hand cart structure over the useful life; as well as simplifying the method of manufacturing and assembling the desired hand cart.